Air filter operable for filtering cabin air in vehicles, agricultural machinery, construction equipment and other work machines

ABSTRACT

The invention relates to an air filter element of a passenger compartment for the driver&#39;s cab of agricultural and work machines, in particular with spraying and atomizing devices for pesticides and fertilizers, having an adsorption filter layer with activated carbon, a fine filter layer in particular for separating aerosols and a circumferential sealing for separating the raw side from the clean side during installation into a filter housing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/939,678 filed 11 Jul. 2013 which claims priority to U.S. ProvisionalPatent Application No. 61/733,550 filed Dec. 5, 2012 and further claimsforeign priority to German Patent Application no. 10 2012 013 671.4filed Jul. 11, 2012. The entire disclosure of U.S. application Ser. No.13/939,678 is incorporated herein by reference.

TECHNICAL FIELD

The invention relates to a passenger compartment air filter for the airsupplied to a driver's cab in agricultural machines, constructionmachines, and work machines.

BACKGROUND OF THE INVENTION

An air filter, which combines an outer layer of activated carbon with alayer of a HEPA filter, is known from WO 00/33940 A1.

However, the filtering effect of this filter may not be sufficient forapplications in which, for example, high pesticide concentrations or(liquid) fertilizer concentrations occur in ambient air, especially whendealing with sprayers for these substances. This may be particularlydisadvantageous for drivers or operators when spraying liquid pesticidesand/or fungicides with agricultural or forestry tractors andself-propelled sprayers.

A mixture of liquid floating particles and air is understood as aerosolfor the following embodiments.

It is, therefore, the object of this invention to provide a passengercompartment air filter, which has a better filtering effect in relationto the occurring dusts, aerosols, and vapors, in particular frompesticides and fungicides, during operation of agricultural machines.

SUMMARY OF THE INVENTION

This object is solved by a passenger compartment air filter element,comprising an ad-sorption filter layer, comprising activated carbon, inparticular for separating gases, a fine filter layer, in particular forseparating aerosols, and a circumferential sealing for separating theraw side from the clean side during installation into a filter housing.

The filter element according to the invention can in particular be usedfor the driver's cab of agricultural and work machines, in particularwith spraying and atomizing devices for pesticides or fertilizers. Bycombining adsorption filter layer and fine filter layer, a greatlyimproved air quality inside the driver's cab can be reliably obtained inthe above-mentioned strongly contaminated environments. In theadsorption filter layer, in particular harmful and/or unpleasantsmelling gases are bound, in the fine filter layer disposed upstream ordownstream of the adsorption filter layer, fine dusts, vapors andaerosols are removed from the air. The fine filter layer is preferablydisposed upstream of the adsorption filter layer.

In one embodiment, an inflow-sided prefilter layer, in particular forseparating dusts, is additionally provided. This prefilter layer isarranged upstream of the adsorption filter layer and the fine filterlayer and disposed on the inflow side of the passenger compartmentfilter element. As a result, a reliable functioning of the adsorptionfilter layer and the fine filter layer can be ensured even in very dustyenvironments, and the dust load of the intake air can be reduced.

The activated carbon used may be, for example, obtained from wood oranthracite coal, it can be polymer-based, tar-based or based on coconutshell. In a preferred embodiment, ion exchange beads that aremanufactured on polymer basis, for example of synthetic resins, inparticular of polystyrene cross-linked with divinylbenzene, are used asbasic material for the activated carbon.

In one embodiment, a hydrophobic activated carbon is used as activatedcarbon. As hydrophobic active carbons are in particular understoodthose, which have a comparatively low water absorption capacity.Preferably, an activated carbon is used which has, at a relative airhumidity of 50%, a water absorption of <10 mass percent, in particularbased on the adsorption branch of the isotherm. Particularly preferred,this water absorption is <5 mass percent.

In one embodiment, the activated carbon features a BET surface of largerthan

400 m²/g, advantageously larger than 600 m²/g, preferably larger than800 m²/g, particularly preferred larger than 1000 m²/g (preferablymeasured according to DIN ISO 9277:2003-05). As a result, a sufficientadsorption can be ensured even on a small mounting space.

In one embodiment, activated carbon is used in loose or pourable form,for example in the form of granular or spherical or otherwise shapedparticles. The activated carbon particles feature preferably activatedcarbon particle sizes (average diameter) between 0.1 and 1 mm,preferably 0.2 to 0.7 mm and they may, for example, have the shape ofgranulated activated carbon or spherical activated carbon.

In one embodiment, an unfolded or zigzag-folded filter medium can beused as prefilter layer. This can, for example, consist of cellulose,synthetic foam or fleece or comprise one single- or multi-layercombination of layers of such filter media.

A synthetic foam filter media layer for the prefilter layer may be, forexample, made of a reticulated foam, in particular polyurethane foam,for example on polyether or polyester basis, or may comprise one or morelayers of this foam. Volumetric weights of such foams can range from20-70 kilograms per m³.

As cellulose filter medium for the prefilter layer may, for example, acellulose filter medium with epoxy impregnation be used. Preferably, thecellulose filter medium has a grammage of 80-140 g/m², preferably100-120 g/m². In one preferred embodiment, the medium features a maximumpore size in the range from 30-40 μm and/or an air permeability ofapprox. 100-400 l/m²s, preferably between 200 and 300 l/m²s, measuredrespectively with a pressure differential of 200 Pa (measured here andin the following preferably according to DIN EN ISO 9237). By so doing,the subsequent layers can be protected from dust deposit and theirfunctioning can therefore be ensured. In one embodiment, theimpregnation percentage, i.e. the proportion of weight of theimpregnating agent of the filter medium grammage is between 15 and 30%.

A combination of a spunbond fleece layer and a meltblown layer (fleeceof meltblown synthetic fibers) can preferably be used as fleece filtermedium for the prefilter layer. Both layers can each be made ofpolyamide (PA), polyester (PES) or polypropylene (PP). The fleece filtermedium features preferably a grammage between 60 and 140 g/m²,preferably between 80 and 120 g/m² and/or a thickness in the range of0.5-1 mm, particularly preferred of 0.5-0.8 mm. The air permeability isfurther preferred in the range of 1000-2000 l/m²s, particularlypreferred between 1200 and 1800 l/m²s with a pressure differential of200 Pa.

In one embodiment, the prefilter layer in particular according to ISO5011 features a degree of separation of 99% for fine test dust PTI inparticular according to ISO 14269-4.

The prefilter layer features in one preferred embodiment a grammage of75-125 g/m². Preferably, the filter medium of the prefilter layerfeatures an air permeability of 100-200 l/m²s with a pressuredifferential of 200 Pa.

By using the prefilter layer it is possible to protect the adsorptionlayer and the fine filter layer against a too high dust load. As aresult, its functionality (gas separation of the adsorption layer andaerosol separation of the fine filter layer) suffers only minorimpairment even if the intake air is very dust-loaded.

An open-pore foam with pourable activated carbon can, for example, beused for the adsorption filter layer. In this case, reticulated foams,e.g. made of synthetic material such as polyurethane, polyurethane etheror polyurethane ester are, for example, used. Preferably, the foam'spore sizes are between 20 and 50 ppi (pores per inch) or between 0.5 and2 pores per millimeter. Measurements are made with a comparative opticalmethod, wherein a fully developed pore is defined as “standard pore”under the microscope and the pores emerging over a track section arecompared with this standard pore and counted. Pores, which are notcompletely developed compared with the standard pore, are counted on apro rata basis Preferably activated carbon particles are introduced andpreferably fixed in this foam. In doing so, the activated carbonparticles are preferably fixed in the foam by means of adhesive, forexample by means of a two-component adhesive on polyurethane basis. Thiscan, for example, be obtained by soaking the foam first with an adhesiveand subsequently pouring activated carbon particles into the foam inparticular by vibration, before the adhesive dries or hardened. In thisconnection, a two-component adhesive, a hotmelt adhesive or an aqueousadhesive can be used.

In one embodiment, a layer of a fixed bulk with activated carbon is usedas adsorption filter layer. This can be realized in a single-layer ormulti-layer structure. An arrangement, in which a carrier stratum isprovided and on which a bulk layer of activated car-bon particles isfixed, is called fixed bulk. For example, an expanded synthetic grid ora layer of a flat material, for example of a particle filter medium, canbe used as carrier stratum. In a preferred embodiment, a fleece ofspunbond or meltblown polyester fibers, for example PET fibers(polyethylene terephthalate) or PBT fibers (polybutylene terephthalate)is used as carrier stratum. This can feature a grammage between 25-120g/m², preferably between 50-100 g/m², particularly preferred between65-85 g/m², and an air permeability>3000 l/m²s, preferably >5000 l/m²swith a pressure differential of 200 Pa. The air permeability is measuredin particular according to ISO 9347. The bulk layer of activated carbonparticles is applied on the carrier stratum and preferably fixed on thecarrier stratum by means of a fine adhesive application. This is, forexample, done in the form of a plurality of adhesive dots applied on thecarrier stratum or by means of a net of adhesive threads which isapplied between carrier stratum and bulk layer and/or between the bulklayer during the pouring and/or on the bulk layer. The bulk layercomprises preferably a layer of 100-1200 g/m² activated carbon particleson the carrier stratum. Preferably, between 800 and 1000 g/m² are used.The layer of a fixed bulk with carrier layer and bulk layer featurespreferably an air permeability in the range of 800-1200 l/m²s, inparticular between 900 and 1100 l/m²s, and a grammage in the range of850 to 1250 g/m², in particular between 950 and 1150 g/m² with a layerthickness in particular in the range of 2 to 6 mm.

By so doing, a stable, easy-to-process and efficient layer of a fixedbulk is provided which can be combined by a machine to multi-layersemi-finished products.

In one embodiment, an unfolded or zigzag-folded stratum structure of acarrier stratum, a cover stratum and pourable activated carbonintroduced therebetween is used for the adsorption filter layer. As aresult, a semi-finished product with a carrier stratum and a coverstratum and a bulk layer disposed therebetween is formed. Suchsemi-finished products can, in turn, be arranged one above the other toincrease the filtration performance, for example between two and 20semi-finished products, preferably between 5 and 15 semi-finishedproducts.

The cover stratum can be disposed directly on the bulk layer, andcomprise, for example, a synthetic grid or a layer of a flat material,for example of a particle filter medium, or consist thereof. In apreferred embodiment, a fleece of spunbond or meltblown poly-esterfibers is used as carrier stratum. This can feature a grammage between25-120 g/m², preferably between 50-100 g/m², particularly preferredbetween 65-85 g/m², and an air permeability>3000 l/m²s, preferably >5000l/m²s.

In one embodiment, the adsorption filter layer features a stratumstructure of several fixed bulks For example, a first layer of a fixedbulk can be placed with the side, on which the activated carbon isdisposed (activated carbon side), on the activated carbon side of asecond layer of fixed bulk and connected with it, for example by gluing.As a result, a semi-finished product with two carrier strata or coverstrata and a bulk layer disposed therebetween is formed. Suchsemi-finished products can, in turn, be arranged one above the other toincrease the filtration performance, for example between two and 10semi-finished products, preferably between 3 and 7 semi-finishedproducts. As an alternative or in combination, assemblies are alsoconceivable in which the carrier layer of a layer of a fixed bulk isplaced on the activated carbon layer of another fixed bulk. Thisassembly can then be finished by a turned layer with fixed bulk or by acover stratum. For example, between 4 and 20 layers of a fixed bulk canbe arranged one above the other.

In one embodiment, the complete adsorption filter layer can form azigzag-folded stratum structure or comprise individual, superimposed,separately folded or unfolded strata of semi-finished products or layersof fixed bulk.

Preferably, by means of the described variants several adsorption filterlayers in stratum structure arranged one above the other, comprising acarrier stratum, a cover stratum and pourable activated carbonintroduced therebetween, can form a complete adsorption filter layer. Inparticular between 2 and 30, preferably between 5 and 15 layers ofsemi-finished products or of fixed bulk are arranged one above the otherto form the complete adsorption filter layer and optionally connectedwith each other sealingly by means of a fastener, for example a lateralstrip made of fleece or textile, to form a partial adsorption filter. Inthis case, the lateral strip can be connected with the layers by meansof an adhesive. As an alternative to the lateral strip, in particular aglued, injection molded or welded-on synthetic frame or a castingcompound, in particular polyurethane, cast on to the layers by means ofa casting mold can be used as lateral sealing.

In one embodiment, the adsorption filter layer features two areas withdifferent activated carbon density. In this case, an area with higheractivated carbon density is preferably disposed on the outflow side andan area with lower activated carbon density on the inflow side. Thiscan, for example, be obtained by placing two layers of different foamsfilled with activated carbon particles on top of each other, wherein theoutflow-sided layer has a higher filling level of activated carbon thanthe inflow-sided layer. As an alternative, and as described above indifferent variants, a stratum structure of layers with fixed bulks ofactivated carbon particles can be used, in which one or severaloutflow-sided layers or strata, which close in particular the stratumstructure at the outflow side, have a higher activated carbon density.This can, for example, be obtained with the same materials for carrierstrata, bulk layers, and cover layers by calendering the outflow-sidedlayers in particular before, during or after the curing of the adhesivein such a way that the stratum thickness is reduced and therefore theactivated carbon density is increased. However, an activated carbongranulate, which has a higher bulk density than that one used for thelayers with lower density, can be used for the layer(s) with higheractivated carbon density. This can either be realized by activatedcarbon of different specific density or by different particlegeometries. As a result, in particular a barrier layer is realized,which reliably allows the separation of residual concentrations ofharmful gases. As a result, an additional safety can be provided for theuser.

In one preferred embodiment, the adsorption filter layer features anoutflow-sided area comprising one or several in particular calenderedlayers of fixed bulk. This/These lay-er(s) feature(s) preferably a layerof activated carbon of 100-1200 g/m² activated carbon particles on thecarrier stratum. Preferably, between 800 and 1000 g/m² are used. Thelayer of a fixed bulk with carrier layer and bulk layer featurespreferably an air permeability in the range of 800-1200 l/m²s, inparticular between 900 and 1100 l/m²s, and a grammage in the range of850 to 1250 g/m², in particular between 950 and 1150 g/m² with a layerthickness in particular in the range of 1 to 3 mm. These layers or thislayer feature particularly preferred in the outflow-sided area withhigher activated carbon density primarily the same layer of activatedcarbon particles in relation to the grammage and/or the type ofactivated carbon particles than the previous, inflow-sided layers withlower activated carbon density. Furthermore, this layer or these layersfeature preferably a considerable lower layer density than the previous,inflow-sided layers with lower activated carbon density. The layerthickness can, for example, be ⅔ smaller than the thickness of theprevious, inflow-sided layers with lower activated carbon density,preferably between 40% and 60% of the thickness of the previous,inflow-sided layers. To achieve this, for example the layer or thelayers with higher activated carbon density are compressed bycalendering or by a similar method in such a way that, compared with theuntreated stratum, such a reduction in thickness can be obtained. By sodoing, the different areas with different activated carbon density canbe made of the same basic materials, wherein only one additionalcalendering step is required for generating the layers with higheractivated carbon density.

In one preferred embodiment, a bulk of activated carbon particles, whichhas compared with the previous, inflow-sided layers with lower activatedcarbon particles a higher bulk density, is used for the layer or thelayers with higher activated carbon density. In this case, the bulkdensity compared with the inflow-sided layers with lower activatedcarbon density, is preferably 50%, particularly preferred 100% higher.

In one particularly preferred embodiment, a bulk of activated carbonparticles, which has compared with the previous, inflow-sided layerswith lower activated carbon particles a lower average particle diameter,in particular an at least 50% lower average particle diameter,preferably an at least 65% lower average particle diameter, is used forthe layer or the layers with higher activated carbon density.

In one embodiment, the inflow-sided layers with lower activated carbondensity feature activated carbon particles with a particle diameter inthe range of 0.7 to 1.2 mm.

In one embodiment, the layer or layers with higher activated carbondensity feature a bulk of activated carbon particles with a particlediameter in the range of 0.3 to 0.7 mm.

With the described embodiments of the adsorption filter stage, inparticular a uniform distribution of the activated carbon is achieved,which is also ensured for example during the operation under vibrationload. By so doing, a contribution for the provision of a reliable filterelement can be made.

With a filter medium according to the invention for an adsorption filterlayer it is possible to provide in particular a passenger compartmentfilter element with an adsorption filter layer that can be easilyprocessed. It is in particular possible to provide a passengercompartment filter element that achieves a test gas concentration below10 μg/g at the outflow side according to the cyclohexane methodaccording to EN 12941:1998 with a test duration of 70 min measuredaccording to EN 15695-2:2009.

In one embodiment, an unfolded or zigzag-folded filter medium with glassfibers in a glass fiber layer is used as fine filter layer. In thisconnection, a glass fiber fleece or glass fiber paper can, for example,be used. This features preferably a one-sided or two-sided laminatedcover stratum made of a spunbonded fleece. As a result, in particular amechanical protection of the often very sensitive glass fiber medium isachieved. This is in particular advantageous if the glass fiber layer isfolded, for thanks to this in particular the medium can be protectedagainst damages, which could lead to local leakages or cracks.Furthermore, such cover strata allow to improve the mechanical strengthof the fine filter layer.

In one embodiment of the fine filter layer, the glass fibers feature afiber diameter in the range of 800 nm to 5 μm. Preferably, 90% of thefibers feature a fiber diameter within this range. Preferably, fiberswith fiber diameters are primarily provided in the complete fiberdiameter area. Preferably, the average fiber diameter is availablewithin the mentioned area. The fiber diameters can, for example, bemeasured according to the methods described in DE 10 2009 043 273 A1 orUS 2011/0235867 A1. Preferably, the filter medium of the fine filterlayer features a grammage between 60 and 100 g/m², particularlypreferred between 75 and 90 g/m². The glass fiber layer featurespreferably a thickness of 0.2-1 mm, particularly preferred of 0.3-0.6mm. Particularly preferred is the use of a glass fiber layer, whichgenerates a resistance in the range of 300-600 Pa, preferably between400 and 500 Pa with an inflow velocity of 7.5 cm/s. The air permeability(permeability) is preferably in the range from 25 to 45 l/m²s, with apressure loss of 200 Pa. The pressure loss with a flow velocity of 5.3cm/s is preferably in the range of 200-700 Pa, particularly preferredbetween 450 and 600 Pa or as an alternative between 270-480 Pa. The poresize can preferably be in the range between 5 and 12 μm, particularlypreferred between 8 and 10 μm.

In one embodiment, the spunbonded fleeces of the cover stratum(strata)are made in particular of a polyester or polypropylene or polyamide asmaterial.

In one embodiment, the spunbonded fleeces of the cover stratum(strata)feature grammages in the range of 10 and 250 g/m², preferably 20 to 60g/m² and particularly preferred 30-34 g/m². Preferred stratumthicknesses for the cover strata are in the range of 0.1 to 0.3 mm.

In one embodiment, the spunbonded fleece of the cover strata is made ofcontinuous fibers, which are stretched by means oftemperature-controlled air and/or godets and deposited in a tangledmanner on a conveyor belt. A calendering process may follow optionallyfor generating a fiber composite and/or for influencing the fleecesurfaces.

Instead of glass fibers, synthetic fibers can also be used for the finefilter layer. In one example of an embodiment, such a synthetic HEPAmedium is used instead of the described glass fiber media. In this case,polyester or polypropylene or polyamide can, for example, be used asmaterial, in this case, the fiber layers are preferably designed infleece shape and, for example, manufactured in the electro-spinningprocess, in the meltblown process or in any other manner. In this case,an electret medium is preferably used. Due to the material properties ofsynthetic filter media, cover and protective layers are advantageouslynot needed. Preferably, a layer of meltblown fleece made of polyesterwith a grammage of, for example, 80-160 g/m², preferably between 80 and120 g/m² and a thickness of, for example, approx. 0.4 to 1 mm is used.Furthermore, it is preferably applied to a carrier layer. As carrierlayer is, for example, a synthetic sup-port grid or a spunbonded fleecelayer taken into account. The other properties can correspond to thoseof the described fine filter layers with glass fibers.

In one embodiment, the prefilter layer and the fine filter layer areintegrated in a filter bellows with in particular directly superimposedlayers of a prefilter medium and a fine filter medium.

In one embodiment, one cover stratum is laminated only one-sided ontothe glass fiber layer, the prefilter medium is directly laminated ontothe other side. This layer combination can either be integrated in aflat manner into the passenger compartment filter element orzigzag-folded as complete layer combination and form a bellows. By sodoing, a passenger compartment air filter element with several filterlevels can be provided with little installation effort and on a smallmounting space.

Cover strata and/or prefilter layer can be applied to the glass fiberlayer in different ways. In this connection, for example sprayedadhesives, for example in aqueous suspension, for example on PU basis,are used. As an alternative, sprayed, in powder application processes orapplied hotmelt adhesives, for example in the form of adhesive fleecesor grids, can be used between the layers, which melt in a fixing stepduring calendering and harden subsequently and thus realize a durableconnection. In this way, a reliable connection can in particular berealized between glass fiber layer and cover strata, which allows afolding of the filter medium.

With a filter medium according to the invention for a fine filter layerit is possible to pro-vide in particular a passenger compartment filterelement with fine filter layer that can, in particular, be easilyprocessed to form a bellows. In particular, a passenger compartmentfilter element can be provided, that achieves an aerosol penetration of0.05% measured according to EN 15695-2:2009.

In the filter element according to the invention, prefilter layer and/orthe adsorption filter layer and/or the fine filter layer can each form aseparate partial filter element or completely or partially connectedwith each other consecutively in layers.

In a preferred embodiment, the passenger compartment filter elementcomprises consecutively at least two of the three partial filterelements prefilter layer, adsorption filter layer, and fine filterlayer. They feature each preferably a lateral strip surrounding thecircumferential narrow sides, which is sealingly connected with therespective partial filter layer. The lateral strip can be a textilelateral strip or made of fleece.

Preferably, the sides of the filter layer, which are not flowed through,are in this case designated as narrow sides. In this case, the narrowsides surround the inflow and out-flow sides or surfaces, respectively,In a media structure which is formed of zigzag-shaped folds of a medium,the notion narrow sides comprises the surfaces (front faces) formed bythe zigzag-shaped course of two edges of the medium as well as the endsurfaces running parallel to the fold edges.

In one embodiment, the prefilter layer and/or the adsorption filterlayer and/or the fine filter layer are directly placed one above theother and zigzag-folded as unit.

In one embodiment, the partial filter elements for forming the passengercompartment filter element are in particular placed directly one abovethe other and sealingly connected by means of a frame, in particular bymeans of a lateral strip surrounding the common narrow side, inparticular made of fleece or textile, which can be welded or glued withthe partial filter elements.

As an alternative, in particular an injection molded synthetic frame canbe provided. It can either be prefabricated and receive the partialfilter elements which are glued in the frame or welded. As analternative, the frame can be designed as overmolded frame which isformed in this way that the partial filter elements are laid into a moldand subsequently overmolded with an injection molded frame, wherein thematerial is undetachably connected with the partial filter elementduring hardening.

Furthermore, as an alternative, the frame can be formed of a castingcompound of polyurethane (PUR) or another pourable polymer, inparticular of a foamed polyurethane, i.e. polyurethane foam.

In one embodiment, the sealing is made of a circumferential sealingprofile of a polymer, in particular of a foamed, in particularclosed-pore foam for example of polyurethane foam. If the frame is alsomade of such a material, the sealing can be designed as one piece withthe frame. Preferably, the sealing features a hardness in the rangebetween 5 and 45 Shore A, particularly preferred of 13+/−4 Shore A.

In a preferred embodiment, the sealing is axially or radially sealinglycompressible or fixable between two housing components of a filterhousing.

The invention relates to a passenger compartment air filter system forthe driver's cab of agricultural and work machines, in particular withspraying and atomizing devices for pesticides or fertilizers, comprisinga passenger compartment air filter element according to the inventionand a housing with an air intake and an air outlet, in which thepassenger compartment air filter element sealingly separates the inletside from the outlet side.

The invention relates further to a driver's cab of a vehicle or a workmachine comprising a passenger compartment air filter system accordingto the invention as well as the use of a passenger compartment airfilter element according to the invention or a passenger compartment airfilter system in a driver's cab of a vehicle or a work machine.

Further possible implementations of the invention comprise also notexplicitly mentioned combinations of characteristics of the passengercompartment air filter element or the passenger compartment air filtersystem described previously or in the following with respect to theexamples of an embodiment. In this context, the person of skill in theart will add or modify also individual aspects as improvements orcomplements to the respective basic form of the invention.

Further embodiments of the invention are subject of the subclaims aswell as of the examples of an embodiment of the invention described inthe following. Furthermore, the invention is explained in detail basedon examples of an embodiment with reference to the attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying Figures, where like reference numerals refer toidentical or functionally similar elements throughout the separate viewsand which together with the detailed description below are incorporatedin and form part of the specification, serve to further illustratevarious embodiments and to explain various principles and advantages allin accordance with the present invention.

Features of the present invention, which are believed to be novel, areset forth in the drawings and more particularly in the appended claims.The invention, together with the further objects and advantages thereof,may be best understood with reference to the following description,taken in conjunction with the accompanying drawings. The drawings show aform of the invention that is presently preferred; however, theinvention is not limited to the precise arrangement shown in thedrawings.

It is shown in:

FIG. 1: a layer of a fixed activated carbon bulk on a carrier stratum;

FIG. 2: a first embodiment of a semi-finished product of an adsorptionfilter layer made of two layers according FIG. 1;

FIG. 3: a second embodiment of a semi-finished product of an adsorptionfilter layer made of two layers according FIG. 1;

FIG. 4: a semi-finished product of an adsorption filter layer made of alayer ac-cording to FIG. 1 and of a cover stratum;

FIG. 5: an adsorption filter layer made of two layers of a semi-finishedproduct according FIG. 4;

FIG. 6: a passenger compartment air filter system with an embodiment ofa passenger compartment air filter element;

FIG. 7: as an example the adsorption and desorption properties for waterof an activated carbon material;

FIG. 8: a passenger compartment air filter system with a furtherembodiment of a passenger compartment air filter element; and

FIG. 9: a passenger compartment air filter system with a furtherembodiment of a passenger compartment air filter element.

Skilled artisans will appreciate that elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions of some of the elements inthe figures may be exaggerated relative to other elements to help toimprove understanding of embodiments of the present invention.

DETAILED DESCRIPTION

A possible structure of an adsorption filter layer can be taken fromFIGS. 1-5. FIG. 1 shows a layer 100 of a fixed bulk of activated carbonparticles, comprising a carrier stratum 101 and a bulk layer 102 withactivated carbon particles.

Two of these layers can be connected in different ways to formsemi-finished products, which can form a single-layer or multi-layeradsorption filter layer. In the embodiment according to FIG. 2, two suchlayers 100 are arranged one above the other in such a way that the bulklayers 102 are superimposed, wherein a semi-finished product is formed,which is limited on both sides by the carrier layers 101. Several ofthese semi-finished products can be placed one above the other to form acomplete adsorption filter layer.

In the embodiment according to FIG. 3, two such layers 100 are arrangedone above the other in the same orientation, however, a greater numberof such layers 100 can be arranged one above the other in this way. Toform a closed adsorption filter layer, a cover stratum 103 can beapplied to the bulk layer 102

FIG. 4 shows an embodiment of a semi-finished product 110 with a layer102 of a fixed bulk of activated carbon particles, which are applied toa carrier stratum 101 and covered by a cover stratum 103. Thesemi-finished product 110 can form a complete adsorption filter layereither in single-layer or, as shown in FIG. 5, in a two- or multi-layerassembly of superimposed semi-finished products 110.

The bulk layers 102 in the embodiments are connected by means of finenets of adhesive threads with the respective carrier and cover strata,however, other connection types can be chosen.

FIG. 6 shows an embodiment of a passenger compartment air filter system70 in a driver's cab 80 for vehicles, agricultural machines,construction machines, and work machines. The passenger compartment airfilter system 70 comprises a housing 50 with a first housing half 51 anda second housing half 52, which are connected with each other by lockingmeans 53. A passenger compartment air filter element 1 (filter element)is disposed in the housing 50 in such a way that the raw side 61 issealingly separated from the clean side 62. The filter element featuresa circumferential sealing 41, which is sealingly compressed bytensioning the filter element 1 between the housing halves axially, i.e.in flow direction 60, against a sealing surface of the second housinghalf. The sealing 41 is designed as a profile poured into a mold ofclosed polyurethane foam with a Shore hardness of 13 Shore A. The filterelement 1 comprises an inflow-sided prefilter layer 10, which definesthe raw side, an outflow-sided fine filter layer 30, which defines theclean side, and an adsorption filter layer 20 disposed therebetween.This can either, as shown at the left with reference numeral 21, be madeof a multi-layer structure of superimposed layers of fixed bulks ofactivated carbon particles on carrier layers or, as indicated besides atthe right, of an open-pore foam with poured-in activated carbon.According to the variant shown under reference numeral 21, seven doublelayers of fixed bulks, as shown in FIG. 2, are superimposed in thisembodiment, which can comprise each a carrier layer made of spunbondedfleece of meltblown PET fibers (polyethylene terephthalate) with agrammage of 85 g/m² and an air permeability of 5500 l/m²s with 200 Pa. Abulk of activated carbon beads of approx. 800 g/m² is applied on it bymeans of an adhesive on polyurethane basis applied in thin fibers. Thisbulk features, with a relative air humidity of 50%, a water absorptionof approx. 9 mass percent and a BET surface of 900 m²/g. The activatedcarbon particles have a diameter in the range of 0.2 to 0.7 mm.According to the variant shown under reference numeral 22, theadsorption filter layer is made of activated carbon particles, whichcomprises an open-pore (reticulated) foam of polyurethane with a poredensity of an average of 40 ppi (pores per inch) or 1.6 pores permillimeter, into which the activated carbon particles used also above invariant 21 with fixed bulks are poured and fixed by means of atwo-component adhesive on polyurethane basis, in which foam is fixed.Both variants feature an extension of 30 mm in through-flow direction.

The prefilter layer 10 is made of a zigzag-folded cellulose filtermedium 11 with epoxy impregnation, which has a grammage of 90 g/m², amaximum pore size of 40 μm, an air permeability of approx. 200 l/m²smeasured with a pressure differential of 200 Pa.

The fine filter layer 30 is made of a zigzag-folded HEPA glass fibermedium 31 with a stratum of a glass fiber paper with cover stratalaminated on both sided made of a spunbonded fleece of polyester. Theglass fibers feature different fiber diameters in the range of 800 nm to5 μm. The grammage of the glass fiber paper is preferably 80 g/m². Thecover stratum has grammages of approx. 30 g/m² and stratum thicknessesof approx. 0.2 mm and is connected with the glass fiber paper by meansof a calendering process.

Prefilter layer 10, fine filter layer 30, and adsorption filter layer 20feature each a sealingly circumferential lateral strip 12, 23, 32 ofpolyester nonwoven and, placed one above the other, they are connectedby means of another lateral strip 40 to form a filter element 1, whereinthe lateral strip 40 sealingly connects the partial filter layers 10,20, 30 with each other. On the other hand, the sealing 41 is foamed ontothe lateral strip 40, with which the raw side can be separated from theclean side in the housing 50.

As an example, FIG. 7 shows the adsorption and desorption properties forwater of an activated carbon material based on isotherms. Plotted on thex-axis is the relative humidity in percentage and on the y-axis thewater absorption W in mass percent relating to the mass of the activatedcarbon. Typically, the measurement is carried out at normal temperatureand normal pressure. The maximum water absorption for many types ofactivated carbon is in the range of 20 to 50 mass percent. Typically,activated carbon shows a hysteresis behavior with adsorption anddesorption, as shown in FIG. 6. The solid line shows the process ofwater absorption with adsorption and is called adsorption branch. Thedashed line shows the process of water absorption with desorption and iscalled desorption branch. According to the invention, the waterabsorption W (50%) with a relative humidity of 50% is smaller than 10mass percent, preferably smaller than 5 mass percent, measured on thesolid adsorption branch of the isotherm.

FIGS. 8 and 9 each show variations of the embodiment shown in FIG. 6,wherein the variation shown in FIG. 8 is characterized by the fact thatas adsorption filter layer 20 a single- or multi-layer stratum structureof fixed bulks of activated carbon is formed, which is zigzag-folded, inparticular in such a way that opposing fold flanks contact one anotherso that no gap is formed between the folds.

The variant shown in FIG. 9 corresponds to the embodiment shown in FIG.6, wherein in that case the fine filter layer 30 is disposed between theprefilter layer 10 and the ad-sorption filter layer 20. This has theadvantage that the adsorption filter layer 20 is charged with an evenlower amount of particles so that its efficiency can well be maintained.Of course, the adsorption filter layer can also be designed in thisvariant as well as in the embodiment shown in FIG. 6 as shown in FIG. 8.

In the foregoing specification, specific embodiments of the presentinvention have been described. However, one of ordinary skill in the artappreciates that various modifications and changes can be made withoutdeparting from the scope of the present invention as set forth in theclaims below. Accordingly, the specification and figures are to beregarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope of thepresent invention. The benefits, advantages, solutions to problems, andany element(s) that may cause any benefit, advantage, or solution tooccur or become more pronounced are not to be construed as a critical,required, or essential features or elements of any or all the claims.The invention is defined solely by the appended claims including anyamendments made during the pendency of this application and allequivalents of those claims as issued.

What is claimed is:
 1. A passenger compartment air filter element forfiltering an air flow in a driver's cab of agricultural and workmachines, comprising: an adsorption filter layer including: a pluralityof individual adsorption layers, each having: a carrier stratum layer ofa flat layer of filter medium or synthetic grid; and a bulk layer ofactivated carbon particles arranged on one side of the carrier stratumlayer, the bulk layer of activated carbon particles layered onto thecarrier stratum layer and fixed to the carrier stratum layer by anadhesive; wherein the plurality of individual adsorption layers arelayered directly upon immediately adjacent individual absorption layers,onto either the carrier stratum layer or the bulk layer of active carbonof the immediately adjacent individual absorption layers, to form theadsorption filter layer; a circumferential sealing element operable forsealably separating a raw side from a clean side of a filter housingwhen installed into the filter housing; an inflow-sided prefilter layerhaving a porosity configured to separate dust from the airflow; a finefilter layer configured for separating aerosols from the air flow, thefine filter layer arranged downstream of the adsorption filter layer atan outflow side of the adsorption filter layer; wherein at least one ofthe following layers is embodied as a separate partial filter element:the prefilter layer, the plurality of individual adsorption filterlayers and/or the fine filter layer.
 2. The passenger compartment airfilter element according to claim 1, wherein the fine filter layer is azigzag-folded filter medium of glass fiber fleece; wherein the finefilter layer includes at least one cover strata made of a spunbondedfleece.
 3. A passenger compartment air filter element for filtering anair flow in a driver's cab of agricultural and work machines,comprising: an adsorption filter layer including: a plurality ofindividual adsorption layers, each having: a carrier stratum layer of aflat layer of filter medium or synthetic grid; and a bulk layer ofactivated carbon particles arranged on one side of the carrier stratumlayer, the bulk layer of activated carbon particles layered onto thecarrier stratum layer and fixed to the carrier stratum layer by anadhesive; wherein the plurality of individual adsorption layers arelayered directly upon immediately adjacent individual absorption layers,onto either the carrier stratum layer or the bulk layer of active carbonof the immediately adjacent individual absorption layers, to form theadsorption filter layer; a circumferential sealing element operable forsealably separating a raw side from a clean side of a filter housingwhen installed into the filter housing; an inflow-sided prefilter layerhaving a porosity configured to separate dust from the airflow; whereinthe inflow-sided prefilter layer is an unfolded or zigzag-folded filtermedium made of cellulose, synthetic foam or synthetic fleece; whereinthe prefilter filter layer comprises two layers, in combination: aspunbond fleece layer of polyamide (PA), polyester (PES) orpolypropylene (PP); and a meltblown fleece layer of polyamide (PA),polyester (PES) or polypropylene (PP).
 4. The passenger compartment airfilter element according to claim 3, wherein at least one of thefollowing layers is embodied as a separate partial filter element: theprefilter layer, the plurality of individual adsorption filter layersand/or a fine filter layer configured to separating aerosols from theair flow and arranged downstream of the adsorption filter layer at anoutflow side of the adsorption filter layer.
 5. The passengercompartment air filter element according to claim 4, comprising: a frameor a lateral strip arranged directly on and fixed onto one or morelateral sides of the air filter element; wherein the circumferentialsealing element is arranged on the frame or on the lateral strip; aplurality of the separate partial filter elements, each according toclaim 4; wherein the plurality of separate partial filter elementsforming the passenger compartment filter element are stacked adjacentlyone above the other and sealingly connected and secured together by theframe or the lateral strip surrounding and joining common narrow sidesof the plurality of separate partial filter elements; wherein the frameor the lateral strip is injection molded onto, or welded to or gluedonto the narrow sides of the plurality of separate partial filterelements.
 6. The passenger compartment air filter element according toclaim 5, wherein the sealing element includes a circumferential sealingprofile comprising any of: a foamed, closed-pore polymer or aclosed-pore polyurethane foam.
 7. The passenger compartment air filterelement according to claim 5, wherein the plurality of individualadsorption filter layers are joined together by a first sealinglycircumferential lateral strip secured to the plurality of individualadsorption filter layers and circumferentially surrounding and joiningtogether the plurality of individual adsorption filter layers forming afirst partial filter element; wherein the prefilter layer includes asecond sealingly circumferential lateral strip secured to the prefilterlayer and circumferentially surrounding the prefilter layer forming thesecond partial filter element; wherein the fine filter layer includes athird sealingly circumferential lateral strip secured to the fine filterlayer and circumferentially surrounding the fine filter layer formingthe second partial filter element; wherein an additional circumferentiallateral strip or plastic frame is overlaid directly onto and secured tothe first, second and third circumferential lateral strips, joiningtogether the first, second and third partial filter elements to form acomplete filter element; wherein the circumferential sealing element isarranged on the additional circumferential lateral strip or plasticframe.
 8. The passenger compartment air filter element according toclaim 1, wherein the fine filter layer is a zigzag-folded filter mediumof glass fiber fleece; wherein the fine filter layer includes at leastone cover strata made of a spunbonded fleece.
 9. The passengercompartment air filter element according to claim 5, wherein theplurality of individual adsorption filter layers are joined together bya first sealingly circumferential lateral strip secured to the pluralityof individual adsorption filter layers and circumferentially surroundingand joining together the plurality of individual adsorption filterlayers forming a first partial filter element; wherein the prefilterlayer includes a second sealingly circumferential lateral strip securedto the prefilter layer and circumferentially surrounding the prefilterlayer; wherein an additional circumferential lateral strip or plasticframe is overlaid directly onto and secured to the first and secondcircumferential lateral strips, joining together the first and secondpartial filter elements to form a complete filter element; wherein thecircumferential sealing element is arranged on the additionalcircumferential lateral strip or plastic frame.
 10. The passengercompartment air filter element according to claim 5, wherein theprefilter layer is a zigzag folded filter medium forming the firstpartial filter element; wherein the plurality of individual adsorptionlayers are each flat, unpleated layers; wherein plurality of individualadsorption layers are stacked directly onto and against each otherforming a flat multilayer adsorption filter as a second partial filterelement of the passenger compartment air filter element; wherein theplurality of stacked individual adsorption layers are joined together toform the second partial filter element; wherein the first separatepartial filter element is arranged on an inflow face of the secondpartial filter element; wherein the first and second partial filterelements are sealingly connected and secured together by the frame orthe lateral strip arranged on and surrounding common narrow sides of theplurality of separate partial filter elements.